Many communication transmission systems, including those for many airborne and ship based satellite systems, need to support multiple RF bands and multiple signal polarizations. For example, some systems need to support two frequency bands where one band can utilize either right and left hand circular polarizations while the other band might only use left hand circular polarization, or only right hand polarization. In other cases where linear polarization is used, the polarization angle into the feed requires frequent adjustment to compensate for platform movement. Linearly polarized signals may need to be either vertically or horizontally polarized based on what satellite resources are available.
Many systems typically do not need to utilize all of the different configurations simultaneously and have been manufactured to switch between configurations so as to minimize cost, weight, and footprint constraints that can be critical when deployed in mobile platforms (e.g., shipboard, aircraft). Any additional hardware needed to provide the switching capability takes valuable space and also must be counterweighted for antenna balance. In some instances, twice the volume is required to implement a multiple configuration capability due to the counterweights.
Some current systems utilize a diplexer on the input to the feed, a waveguide switch, and multiple waveguide sections separately configured to conform with different wavelengths (e.g., waveguide dimensions) to interconnect the switch to the diplexer. Accurate and stable arrangements of the waveguides may thus be necessary so as to avoid unacceptable signal loss (e.g., insertion loss of the transmit path). In yet other implementations, phase matching of the signal paths is needed, which can also introduce further complexity, footprint, and cost.
For example, FIG. 1 is an illustrative block diagram of an exemplary switching system 100. An input waveguide 105 transmits a signal to a “baseball switch” 120. Switch 120 can be configured to polarize a signal through the system 100 by being rotated (depending on the anticipated frequency band and polarization) and thereby connecting the input waveguide 105 with either one of two ports of a diplexer 130 through waveguide 127 or waveguide 125, which are configured to conform with different bands of RF signals, respectively. In this type of configuration, the linear polarization of the signal is determined by the diplexer 130. The signal is subsequently transmitted through the circular polarizer 135 and then to antenna feed horn 140. A drive motor 165 can be utilized to rotate the “baseball switch” 120. This implementation can be very bulky and also will likely need to be counterweighted for proper antenna balance.